1. Field of the Invention
The invention is directed to an injection nozzle for internal combustion engines, and particularly to such an injection nozzle having a blind bore that has at least one injection port, and having a nozzle needle seat adjoining the blind bore.
2. Description of the Prior Art
Blind bore injection nozzles of the type with which the invention is concerned, particularly in the partial stroke range of the nozzle needle, have great variation of the flow resistance and thus also of the injected fuel quantity. As a consequence, the emissions and fuel consumption of many internal combustion engines equipped with these blind bore injection nozzles is other than optimal.
The object of the invention is to furnish a blind bore injection nozzle in which the variation in the injection quantity in the partial-load range of the nozzle needle from one example to another of a blind bore injection nozzle of the same design is reduced, and thus the fuel consumption and emissions of the engines equipped with the blind bore injection nozzle of the invention are improved.
This object is attained by an injection nozzle for internal combustion engines, having a blind bore that has at least one injection port, and having a nozzle needle seat adjoining the blind bore, in which the transition between the nozzle needle seat and the blind bore is rounded.
Because the transition between the nozzle needle seat and the blind bore is rounded according to the invention and thus has a defined geometry, the throttling action of the transition between the nozzle needle seat and the blind bore, which action is definitive in the partial-load range of the nozzle needle, is also defined, and thus between various examples of an injection nozzle of the same design now varies to only a very slight extent. Thus by measurement of the operating performance of a blind bore injection nozzle according to the invention, the operating performance of all the other blind bore injection nozzles of the same design can be predicted with substantially greater precision, and the control of the injection event can be optimized accordingly.
In one feature of the invention, the transition between the nozzle needle seat and the blind bore is rounded with a radius between 0.01 mm and 0.1 mm, preferably between 0.04 mm and 0.06 mm, so that on the one hand the rounding already markedly reduces the variation in the partial-load performance of the injection nozzles, and on the other the rounding can be achieved at little cost.
In a further version of the invention, the blind bore is conical, so that the partial-load performance of conical blind bore injection nozzles is improved.
In a further feature of the invention, it is provided that the blind bore is embodied cylindrically, so that the partial-load performance of cylindrical blind bore injection nozzles is improved as well.
A variant of an injection nozzle of the invention provides that the nozzle needle seat is frustoconical, which results in good sealing action and good centering of the nozzle needle in the nozzle needle seat.
In another version of the invention, the cone angle of the nozzle needle seat is 60xc2x0, so that a good sealing action between the nozzle needle and the nozzle needle seat is attained.
In a further feature of the invention, the cone angle of the nozzle needle is up to 1xc2x0, and preferably from 15 to 30 angular minutes greater than the cone angle of the nozzle needle seat, so that the sealing area is reduced and is shifted into the region of the greatest diameter of the nozzle needle.
Another version provides that the blind bore is a mini blind bore or a micro blind bore, so that the advantages according to the invention can be utilized in these injection nozzles as well.
In another version, the transition between the injection port and the blind bore is rounded, so that the throttling action of the injection port is reduced and varies within a narrower tolerance range.
The object stated at the outset is also attained by an injection nozzle for internal combustion engines, having a blind bore that has at least one injection port, characterized in that the transition between the injection port and the blind bore is rounded. This provision lessens the variation in the operating performance of the injection nozzles.